The principal investigator has developed a novel non-invasive mathematical approach and formula, ApEn, based on the science of Chaos, to analyze heartbeat data. The long-term objective of this proposal is to examine the potential use of ApEn to identify those at risk for SIDS. It is anticipated that ApEn will provide diagnostic and predictive insights otherwise inaccessible to the clinician. Potential applications include fetal distress evaluation, arrhythmia detection, and assessment of "post- dates" pregnancies. ApEn is both mathematically and medically innovative. It encapsulates the amount of patternness in heartbeat into a single number. Advantages over alternative approaches include objectivity, ready computability, breadth of focus, and potential for immediate applicability. A prototype study on neonates has already demonstrated the efficacy of ApEn. Phase I focuses on establishing preliminary normal ranges of ApEn values for the healthy infant, and on specifically tailoring ApEn for infant heart beat analysis. Phase II would establish definitive ranges of ApEn values as markers of infant health, and other ranges as indicative of high potential risk for SIDS. Potential commercial applications include the development of a lightweight, portable device that records and analyzes heartbeat data using the ApEn formula.